(1) Related Applications
This is a continuation-in-part application of U.S. application Ser. No. 06/538,797, filed Oct. 4, 1983, now U.S. Pat. No. 4,569,571.
(2) Field of the Invention
This invention relates to a light emitting information display assembly, and more particularly to an emergency illumination display assembly.
(3) Description of the Product
All public and military structures such as hospitals, schools, warehouses and ships are required to have illuminated signs indicating emergency evacuation routes. Certain standards exist pertaining to visibility, light intensity, lettering size, wording, and fail-safe operation. The National Electrical Code requires that emergency lighting systems be designed and installed so that the burning out of any individual lighting element cannot leave any space in total darkness, and that two or more separate and complete systems with independent power supply, each providing sufficient current for emergency lighting purposes, be supplied.
Some fire codes require that the backup system remain visibly illuminated for a period of up to ninety minutes after a power failure to facilitate evacuation of the premises. The Occupational Safety and Health Administration (OSHA) further requires that any sign designating an emergency egress be designed so that the word "EXIT" is depicted in block lettering, at least six inches high. The strokes of these letters must be 3/4 of an inch in width.
Further, the exit indicator must produce a light output of at least five lux, and be mounted in such a way and location as to afford maximum visibility, and cause minimum confusion during an emergency. Most fire codes also require that these indicators be lit continuously during occupancy.
Most signs of the existing type are illuminated by a pair of twenty watt incadescent lamps. Some contain an additional lamp for backup. Many buildings, structures, and ships have numerous exits, and a single multi-floor structure can contain literally hundreds of exit signs, expensive to install, and consuming thousands of kilowatts of electricity per year to operate and dozens of man hours per year to maintain.
In addition, the heat generated (almost useless during heating season due to conduction through walls and ceilings) must be removed during the air conditioning season. Moreover, at least one or more of the light bulbs can be expected to burn out per year of continuous illumination. With hundreds of these units installed in a structure or vessel, the cost of replacing these bulbs can become quite high. The light bulbs themselves are relatively expensive, as is the cost of the labor involved. It has been estimated by those experienced in the art that each emergency exit sign costs between $70 and $120 per year to operate and maintain.
Few inventions of the prior art can meet all or any specification of the various codes and laws. Fewer still can be retro-fitted to meet these requirements at all. Those that can, can be done so only with a labor and materials cost that rivals or exceeds the cost of the original device.
Of the devices that do meet most regulations, some require their auxiliary backup power from the mains as well, rendering them powerless in the face of an overall power outage.
In those that have a battery powered backup system, the battery pack (necessarily large and heavy) powers one or more incadescent low wattage lamps. These lack both sufficient intensity and/or burn time to be useful during a low visibility emergency such as a smoky fire.
A few types have other light sources such as fluorescent tubes or other types of electro-luminescent panels. The initial cost of these units can be prohibitive. The electrical requirements are much more complicated and maintenance costs are higher. Although another model claims to be explosion proof, when displayed in a hazardous location as defined by National Electrical Codes, it is supplied by mains current and in certain situations it can become hazardous, and is therefore, at least, only explosion resistant.